The Common Hazel is a wind pollinated, monoecious tree. A perfect flower, like those found on Cherry trees, has male and female parts combined but this can lead to self pollination so some trees separate the male and female flower parts. If the separated parts are on the same tree it is known as monoecious (Greek for one household). Alder, Oak, Beech, Birch, Hornbeam and Sweet Chestnut are other examples of monoecious trees.
Hazel catkins – the hazel is a monoecious tree with male flowers on hanging catkins and tiny female bud-like flowers with red stigmas. To see catkins on the closely-related Turkish Hazel click HERE
The male flowers are on yellow catkins that hang down ready to release pollen onto the wind. There may be over 200 unisexual male flowers on a single catkin.
Each maleflower is covered by a scale which lifts when the catkin is ready to release pollen. Underneath each scale there are 4 pairs of green stamens full of pollen. The stamens split open to release pollen for wind dispersal when the conditions are suitable.
The female flowers resemble a bud, with crimson stigmas that protrude when they are ready to receive pollen. The flower buds are located on the branch above the catkin, to avoid self-pollination.
The female flower bud is shown in close-up in this photo. Each bud has several flowers. Each flower has 4 stigmas to collect pollen. If fertilised, each flower will produce one nut, known as a cob.